This invention relates to a vise used to hold a workpiece during machining. More particularly, the invention provides an apparatus for forming a stationary vise member or jaw on a vise, the stationary vise jaw having improved deflection characteristics when loaded from a movable vise jaw.
In the art of machining workpieces, numerical-control equipment is used which makes it possible to produce large numbers of identical pieces in a given amount of time, with any desired features (drilled or bored holes, milled or shaped slots, chased threads, etc.) being produced rapidly, accurately, and with minimal error from desired shapes and positions. The workpiece, which is to be machined, is positioned accurately within a vise between a stationary vise jaw or jaw block and a movable vise jaw or jaw block. The workpiece is secured with the vise by bringing the movable jaw to bear against the workpiece until movement of the movable jaw is sufficiently impeded by contact of the workpiece against the stationary jaw.
In precision machining processes, any movement of the workpiece from its expected position contributes to error of machined surfaces in the workpiece. One source of error that has persisted is attributable to deflection of the stationary vise jaw when clamping forces are reacted through it to secure the workpiece. Commonly, the stationary vise jaw is formed by securing a suitable block of material to the vise surface with at least one threaded bolt. A protruding member such as a key is positioned within a corresponding channel formed in a lower surface of the block to further position the block of material on the vise. The bolt is threaded into the block of material at a position between the key and a surface of the block facing the movable jaw.
Although the stationary vise jaw appears secured to the vise, deflection of the stationary vise jaw occurs when force is applied from the movable vise jaw. This deflection is at least partially attributable to compression of the key within the channel.
It might appear that the problem of stationary vise jaw deflection could be solved by forming a stationary vise jaw from a block of material much larger than the size currently in use, and fastening this block to the vise with a large number of bolts. As is well appreciated by those skilled in the art, however, such an approach would inordinately increase the cost of the vise as well as increase the size of the vise for a given opening between the stationary jaw and the movable jaw.